奥氏体不锈钢埋弧焊拼排焊接试验

CFB(循环流化床)锅炉向大容量超临界参数发展是必然趋势,将会采用奥氏体不锈钢膜式管屏。奥氏体不锈钢膜式管屏的拼排工艺已引起业内人员的重视,针对奥氏体不锈钢的特点,采用埋弧焊工艺进行试验。为奥氏体不锈钢埋弧焊拼排选材及焊接工艺提供了依据,为今后更高等级的锅炉管屏埋弧焊焊接打下了基础。     

蜂窝夹芯板表面加工的平整度分析

蜂窝夹芯结构具有高的比强度、比刚度以及质量轻等优点,被广泛应用于航空航天领域。因此,对其进行力学特性分析具有理论研究和工程应用价值。针对卫星常用的蜂窝夹芯结构板,实验测得夹芯板的表面平整度。根据理论推导得出蜂窝夹芯结构的等效材料参数,利用有限元分析软件MSC.Patran/Nastran进行蜂窝夹芯板的表面平整度分析。对比发现,实验结果和计算分析结果相差为5.9%,表明理论推导的可行性。根据三明治等效理论,提出建立常用规格的蜂窝的等效参数的等效系数库,便于蜂窝夹芯结构的工程应用。     

Tuning of size and luminescence of red Y(V,P)O4:Eu nanophosphors for their application to transparent panels of plasma display

Fabrication of transparent plasma display can be demonstrated by simply applying the scatter-less nanophosphors to the currently available plasma display panel (PDP) scheme. For this goal, the optimization of the nanophosphors with respect to size and luminescence is necessary to produce a uniform, transparent, bright emissive layer. To develop red-emitting nanophosphors suitable for transparent PDP fabrication, we hydrothermally synthesized red-emitting Y(V,P)O₄:Eu nanophosphors having various V/P ratios and Eu concentrations and varied their subsequent annealing condition. When Y_0.94(V_0.5,P_0.5)O4:Eu_0.06 nanophosphor annealed at 1000 °C for 1 h was used, 1.1 μm thick, uniform emissive layer with a high visible transmittance value of 72% was generated on glass substrate by a conventional screen-printing. Mini-sized test panels of transparent red-emitting plasma display were constructed by combining the rear plate (Y(V,P)O₄:Eu nanophosphor layer/glass) and the front plate used in alternating current (ac)-type PDP structure, and their discharge luminance characteristics were evaluated.     

Nonlinear dynamical analysis of eccentrically stiffened functionally graded cylindrical panels

Based on the classical shell theory with the geometrical nonlinearity in von Karman–Donnell sense and the smeared stiffeners technique, the governing equations of motion of eccentrically stiffened functionally graded cylindrical panels with geometrically imperfections are derived in this paper. The characteristics of free vibration and nonlinear responses are investigated. The nonlinear dynamic buckling of cylindrical panel acted on by axial loading is considered. The nonlinear dynamic critical buckling loads are found according to the criterion suggested by Budiansky–Roth. Some numerical results are given and compared with the ones of other authors.     

Static and dynamic analysis of an FGM doubly curved panel resting on the Pasternak-type elastic foundation

The static, dynamic, and free vibration analysis of a functionally graded material (FGM) doubly curved panel are investigated analytically in the present paper. The FGM Panel is originated from a rectangular planform and its principle curvatures are considered to be constant. All mechanical properties of the FGM panel are assumed to vary continuously through the thickness according to a power law formulation except Poisson’s ratio, which is kept constant. A Pasternak-type elastic foundation containing damping effects is considered to be in contact with the panel during deformation. The elastic foundation reacts in both compression and tension. Equations of motion are established based on the first order shear deformation and the modified Sanders shell theories. Following the Navier type solution, the established equations are reduced to time-dependent ordinary differential equations. Using the Laplace transform, the time-dependency of the problem is eliminated. The solutions are obtained analytically in the Laplace domain and then are inverted to the time domain following an analytical procedure. Finally, the analytical results are verified with those reported in the literature.     

Analysis and design of the flexible composite membrane stretched on the spacecraft solar array frame

Nonlinear analysis of the deformation of a thin flexible composite membrane stretched on a rectangular cell of the spacecraft solar array frame is presented in the paper. The frame of the array and the thin flexible membrane stretched on this frame are designed to be capable of withstanding the transverse mechanical loadings exerted on the structure during the delivery to orbit and deployment. The governing nonlinear equations modelling the pre-stretched flexible orthotropic membrane are solved using Galerkin method. Results of calculations are compared with those based on finite-element modelling. The comparisons have demonstrated efficiency of the proposed approach to the analysis and design of composite solar arrays featuring orthotropic composite flexible membranes. The parametric analyses were performed for various combinations of the g-force, mass of the photovoltaic elements and dimensions of the solar array.     

Cryogenic reliability of composite insulation panels for liquefied natural gas (LNG) ships

The major carrier of liquefied natural gas (LNG) is LNG ships, whose containment system is composed of dual barriers and composite insulation panels. The LNG containment system should have cryogenic reliability and high thermal insulation performance for safe and efficient transportation of LNG. The secondary barrier composed of adhesive bonded aluminum strips should keep tightness for 15 days, when the welded stainless primary barrier fails. However, cracks are generated in the composite insulation panels due to the local stress concentration and the brittleness of insulation materials at the cryogenic temperature of −163 °C. If cracks generated in the insulation panel propagate into the secondary barrier, LNG leakage problem might occur, which is a remaining concern in ship building industries.In this study, crack retardation capability in the composite insulation panel was investigated with glass fabric reinforcement. Finite element analysis was conducted to estimate the thermal stress at the cryogenic temperature and a new experimental method was developed to investigate the failure of secondary barrier of composite insulation panel. From the experimental results, it was found that the glass fabric reinforcement was effective to retard the crack propagation into the aluminum secondary barrier from the polyurethane insulation foam at the cryogenic temperature.     

Geometric Imperfection Sensitivity of Curved Panels Under Combined Compression and In‐Plane Bending – A Study Using Adaptive Meshing and DIC

Abstract: The existence of geometric imperfections, either resulting from the use of manufacturing tolerances or because of damage in situ is known to have a detrimental effect on the buckling and post‐buckling behaviour of thin‐walled structures, which depending upon factors such as geometry and loading, can be significant. This paper presents an automated technique, based on the use of topography data obtained from optical measurement, for creating finite meshes representative of the geometry of real structures, which can be analysed to obtain accurate predictions of unstable behaviour. The technique incorporates an algorithm to allow mesh density to be varied across the specimen according to level of curvature thus ensuring the meshes generated are not only accurate but also computationally efficient by reducing the number of degrees of freedom where appropriate. The results of applying this technique to a series of curved panels subject to combined shear and in‐plane bending (an example of a component of an aero engine blade) are reported.     

基于缝隙特征的蜂窝夹层结构刚度损失评估及应用

高精度蜂窝夹层结构反射面板由经过开缝应力释放工艺处理的表层铝板和铝蜂窝芯胶接而成, 为了研究缝隙所引起的夹层结构刚度损失, 基于对实验数据的统计分析, 考虑缝隙面积和分布等对刚度的影响, 定义了缝隙对刚度的影响系数与刚度的损失系数并建立了二者之间的关系, 提出了基于缝隙特征的蜂窝夹层结构刚度损失的评估方法。实验分析结果表明, 缝隙对夹层结构刚度造成的损失达到一定程度后明显减缓, 刚度最大损失可限定在40%。针对表板带有缝隙的夹层结构的数值分析, 依据夹层结构刚度等效原则, 利用刚度损失与缝隙影响系数之间的关系, 可将带有缝隙的表板等效为厚度减薄的连续表板, 对于模拟带有缝隙的夹层结构具有一定的应用价值。     

井温对螺杆钻具使用性能的影响

对井底温度引起螺杆钻具定子橡胶的变化进行了理论分析,利用模拟加热试验方法找出定子橡胶尺寸随温升的变化规律。提出改进橡胶配方、选择合适的粘接剂及合理配置过盈量的方法,可以有效地提高螺杆钻具的扭矩,延长螺杆钻具使用寿命,避免掉胶等质量事故的发生,对于螺杆钻具的合理配置和选型有一定的借鉴意义。